Method of recovering hydrocarbons



y 19447 L w. A. HEATH I METHOD OF RECOVERING HYDROCARBQNS Filed Nov. 10, 1941 o OUTPUT WELLS o 'INPUII' WELLS INVENTOR WILLIS A. HEATH BY flake,-

O OUTPUT WELLS 0 INPUT WELLS "7 ORNEY vciris byway oi the open pores. Thus, fluid, which has entered or which was already com tained in the blind pores becomes trapped therein, from. which it cannot be recovered unless the principal direction of fluid flow in thereser= voir is-changed.

In order to change the direction of flow of the injected fluid and thereby recover the oil which is trapped in the blind pore regions or the formation, I shut in output wells 292, 23, 24, 25,26, and 21, withdrawingno fluid therefrom; I open input wells l and H to the atmosphere so that the pressure on the well approaches atmospheric pressure; I maintain input wells ill, ii, iii, and at a superatmospheric injection pressure or P; I maintain a reduced superatmospherlc pressure of p, on input wells ll, it, it, l6, l9, and it. This reduced pressure, p, may be any desired superatmospheric pressure less than pressure P, however, I have found that by maintaining the reduced superatmospheric pressure approximately one-half of the injection pressure I obtain sat isfactory performance of my method. By thus adjusting the pressures on the input wells, the principal movement of fluid through the reservoir will be in the general direction of input wells l5 and H, as indicated by the large full arrows on Figure 1. A minormovement of fluid also takes place between the input wells which are subjected to pressure P and the input wells which are subjected to pressure 1:. There is also a minor move ment of fluid between this latter group of wells and the input wells which are open to the atmos phere. These minor movements are indicated by the small full arrows on the drawing. It will be noted that the direction of flow from all input wells is changed, excepting that from wells ill, l2, l8, and 20. By changing the direction of 'movement of fluid through .the reservoir for a prede termined length of time, as predicted by the reservoir conditions, hydrocarbon oil which was trapped in the blind pores by the movement of fluid through the reservoir previous to the initiation of my instant method is removed from those pores and is caused to flow into the open interconnected pore spaces through which it may be urged to the output wells, when the conventional method of fluid-drive is resumed. Prior to resuming the conventional method of fluid-drive,

- a step in which input wells it and I6 are opened to the atmosphere is practiced, wells ii, til, it, and 2! are subjected to superatmospheric pressure P; and wells 96, i2, i5, ll, 88, and mare subjectedto superatmospheric pressure, p. Thus, the general direction of the principal movement 'of fluid in the reservoir, which is also maintained for a predetermined length of time, is toward input wells l4 and I6, as indicated by the large broken arrows. It is to be noted that the direction of the principal movement of fluid in the reservoir, which-is toward input wells l4 and it that are opened to the atmosphere, is substantially across the direction of the principal movement of fluid resulting from input wells l5 and H be ing opened to the atmosphere. Minor movements of fluid in the reservoir also take place between those input wells which are subjected to pressure P, and those which are subjected to pressure p, and between the latter input wells and input wells I4 and I6, as indicated by the small broken arrows. During the step of my instant invention in which input wells [4 and iii are opened to the atmosphere, hydrocarbon oil which has been trapped in the blind" pores that occur in the formation between input wells l0, l2, l8, and 20 enemas and the output wells is caused to flow to the open interconnected pores through which the oil is urged to the output wells, when the conventional method of fluid-drive is resumed. After the direction of fluid movement in the reservoir has been changed by the steps as set forth, all input wells are subjected to the superatmospheric pressure P, and hydrocarbon fluid is withdrawn from output wells 2'2, 23, 24, 25, 2d, and 2'5. Fluid is injected into all input wells until it again becomes necessary to repeat the steps of my instant invention.

Turning next to Figure 2 for a description of a modification of my instant invention, it will be noted that the input and output wells are designated by the same reference numerals as in Figure 1. When it is'desired in the practice of fluiddrive operations to apply this modification, output wells 22, 23, Hi, 25, 2d, and 2? are shut in. Input wells, i5, i6, and ll are opened to the atmosphere and sufllcient fluid is injected into input wells it, it, l2, it, it, 59, ill, and 25 to maintain a superatmospheric pressure P, thereon. This pressure is preferably that at which normal fluid-drive operations were carried out. The movement of fluid in the reservoir is efiected between the last mentioned group of input wells and the input wells which are opened to the at-- mosphere for a predetermined length of time as predicated by the reservoir conditions in order to remove hydrocarbon oil from the blind pores. The general direction of the movement of the fluid in the reservoir is indicated by the large full arrows on'Figure 2. Minor fluid movements are generally indicated by the small full arrows on Figure 2. Next input wells ill, id, it, l2, l6, and Eli are opened to the atmosphere and input wells ll, i5, i9, 33, ll, and 28 are subjected to the superatmospheric pressure P, and fluid is moved through the reservoir toward the input wells which are open to the atmosphere, as generally indicated by the broken arrows. When the hydrocarbon oil, which has beentrapped in the blind pores of the formation has been removed therefrom to the open interconnecting pore spaces, fluid is again injected into input wells it, it, i8, l2, l6, and 2t, increasing the pressure on these wells to superatmospherie pressure P while continuing to maintain the remaining input wells, namely, wells it, l5, l9, l3, ll, and M at said superatmospheric pressure, P; output wells 2'2, 23, 2d, 25, 2 5, and 21 are opened up to production; and normal fluid-drive operations are resumed. When oil again becomes trapped in the blind" pores, the practice of this modification of my invention'may be resumed.

From the foregoing, it is believed that the many advantages obtainable by the practice of the present invention will be readily apparent to persons skilled in the art. However, since certain changes may be made in carrying out the above method without departing from the scope of the invention as defined by the appended claims, it is intended that all matter contained herein shall be interpreted as illustrative and explanatory, rather than in a limiting sense.

I claim:

1. In a method of recovering hydrocarbons from a hydrocarbon-bearing formation that is substantially devoid of natural fluid energy and that is penetrated by a. plurality of input wells and at least one output well, the steps comprising shutting in the output well,,inlecting fluid under pressure into the formation through at least one input well to efiect movement of hydro.

carbons through the formation in one general direction and toward the output well, subsequently injecting fiuidunder pressure into the formation through at least another :input-wellto effect movement of hydrocarbons through the formation toward the output well in a general direction that is across the direction of movement effected by the preceding step, and opening the previously shut-in well and "withdrawing fluid from the formation therethrough.

2. In a method of recovering hydrocarbons from a hydrocarbon-bearingtformation that is substantiallydevoid of natural fluid energy and that is penetrated by a plurality of input wells and at least tone output well, ;the steps comprising shutting in the output well, injecting fluid under pressure into the formation through at least one input well while maintaining the pressure on at least another of the input wells at an inferior pressure to obtain directional fluid drive and movement of hydrocarbons through the formation and toward the output well, subsequently injecting fluid undensufllcient pressure into the formation through at least one input well other than the first mentioned input well to obtain fluid drive and movement of hydrocarbons through the formation and toward the output well across the fluid drive and movement of hydrocarbons obtainedin the second step, and then withdrawing fluid from the formation through the previously shut-in output well.

3. In a method of recovering hydrocarbons from a hydrocarbon-bearing formation that is substantially devoid of natural fluid energy and that is penetrated by a plurality of input wells and at least one output well, the steps comprising shutting in the output well, injecting fluid under superatmospheric pressure into the formation through at least one input Well while maintaining at least another of the input wells at substantially atmospheric pressure to obtain directh ial movement of the hydrocarbons through the formation and toward the output well, sub- I sequently injecting additional fluid under sumcient pressure into the formation through at least one input well other than the firrt mentioned input well to obtain movement of the hydrocarlbons through the formation and toward the output well across the movement of the hydrocarbons obtained in the second step, and then opening the previously shut-in output well and recovering fluid th'erethrough.

4. In a method of recovering hydrocarbons from a hydrocarbon-bearing formation that is substantially devoid of natural fluid energy and that is penetrated by a plurality of input wells and at least one output well, the steps comprising shutting in the output well, injecting fluid under superatmospheric pressure into the formation through at least one input well while maintaining at least another of the input wells at substantially atmospheric pressure to obtain directional movement of the hydrocarbons through the formation and toward the output well, subsequently injecting additional fluid under superatmospheric pressure into the formation through at least one input well other than the first mentioned input well while maintaining another of the input wells at substantially atmospheric pressure to obtain movement of the hydrocarbons through the formation and toward the output well in a direction across that obtained in the second step, and then opening the previously shut-in output well and recovering 'fluid therethrough. v

5. The method of workingan oilfleld to recover oil from a partially depleted oil-bearing formation that is substantiallyvdevoid of natural fluid energy .and that is penetrated by a plurality of input wells and output wells comprising shutting *in the output wells, injecting fluid under superatmospheric pressureiinto the formation through a group of input xwells while maintaining at least one input well at reduced pressure to move oil in the formation towards one part of the field, subsequently injecting fluid under supera'tmospheric pressure into another group of input wells to move oil :in the formation toward another part of :thezfleld, and withdrawing oil through at least one output well.

6. The method of working an oil field to recover 011 from a partially depleted oil-bearing formation that penetrated a plurality of input wells and output wells comprising shutting in the output wells, injecting fluid under superior ,superatmospheric pressure into the formation through a group :of input wells, simultaneously injecting fluid under inferior superatmospheric :pressure into the formation through a second group of input wells while maintaining a plu- ;raiity of the input wells at a pressure below *said inferior superatmospheric pressure to move -oil through the formation toward one part of the field, subsequently injecting fluid under superior superatmospheric pressure into the for-, .mation through a third group of input wells, simultaneously with the preceding step injecting fluid under inferior superatmospheric pressure into the formation through a fourth group of input wells to move oil through the formation toward another part of the field, and withdrawing oil through output wells.

'7. The method of working an oil field to recover oil from a partially depleted oil-bearing formation that is penetrated by a plurality of input wells and output wells comprising shutting in the output wells, injecting fluid under superior superatmospheric pressure into the formation through a group of input wells, simultaneously injecting fluid under inferior superatmospheric pressure into the formation through a second group of input well while maintaining a plurality of the input wells at atmospheric pressure to moveoil through the formation toward one part of the-field, subsequently injecting fluid under superior superatmospheric pressure into the formation through a third group of input wells, simultaneously with the preceding step in- .iecting fluid under inferior superatmospheric pressure into' the formation through a fourth group of input wells to move oil through the formation toward another part of the fleld, and then withdrawing oil through the output wells.

.8. The method of working an oil field to recover oil from a partially depleted oil-bearing formation that is penetrated by a plurality of input wells and output wells comprising shutting in the output wells, injecting fluid under superatmospheric pressure into the formation through one group of input wells while maintaining another group of input wells at a pressure below said superatmo'spheric pressure to move. oil through the formation toward one part of the field, subsequently injecting fluid under superatmospheric pressure into the formation through a third group of input wells to move oil through the formation toward another part of the fleld, and withdrawing oil through output wells.

9. The method of working a partially depleted, 75 oil-bearing formation that is, penetrated by at least three input Wells that are spaced substantially equidistant and one output well positioned substantially-centrally of the input wells comprising shutting in the output Well, injecting fluid. under superior superatmospherio pressure into the formation through at least one input well while maintaining at least one input well at atmospheric pressure, simultaneously injecting fluid under inferior superatmospherie pressure into the formation through at least one input well to obtain movement of oil through the'for mation in one general direction and toward the output well, injecting fluid under superatmospheric pressure that is greater than the pressure mentioned in the preceding step into the forma= tion through at least one input well first mentioneol other than the well referred to in the second step to obtain movement of oil through the formation and toward the output well in a general direction which crosses the above mentioned direction of movement, and then opening the previously shut-in output well and withdrawing oil therethrough.

WILLIS A. HEATH. 

